Couplings provide the vital link between the elements within a drive train – motor to gearbox or output shaft to driven machinery for instance – and few drive systems would survive without them. Like drive systems, they come in all sizes from enormous to minute and with various performance profiles from precision to power. Drive Lines’ principal coupling manufacturer is R+W in Germany, which offers two ranges: Industrial’ (black), and Precision (white).

Included in the R+W Black range are different types of couplings, each of which has performance characteristics that make it suitable for particular heavy-duty applications. Selecting a suitable coupling and ensuring the optimum size is specified requires skill and experience; this is what Drive Lines provides.

The R+W range includes safety, disc pack, flexible gear, metal bellows and elastomer types.

Safety first

Safety couplings, often referred to as torque limiters, are designed to disengage the drive in the event the load exceeds a safe amount, thus protecting the drive system and possibly the motor, driven load and/or nearby personnel. The simplest form is based on shear pins, sized to break at the torque limit; such designs are not particularly accurate or reliable and need to be rebuilt if they are tripped.

The concept can be taken forward by replacing the shear pins with a sprung ball and detent or plunger mechanism that activates at the set torque to disengage the coupling. The coupling is easily reset. Some mechanisms can be adjusted to specific requirements.

R+W offers safety coupling options that automatically reset after one full revolution of the drive shaft, after rotating a set number of degrees or which require manual resetting, in sizes from 0.2 to 250kNm.

Deforming discs

R+W disc pack couplings transmit torque through thin spring steel discs assembled into a pack and held tightly by pins. Misalignment is accommodated by deformation of the discs. The design is flexible, while remaining torsionally strong under high torque loads and has uses in industrial drives as well as some precision servo applications.

A one-disc coupling can be used where there is no need to allow for parallel misalignment: in a double disc coupling, discs can bend in different directions to better manage any compound offset. Torsionally stiff yet flexible, disc couplings are often used in high speed applications.

R+W offers standard disc couplings from 350Nm to 20kNm, plus bespoke designs, couplings with integral torque sensors and special couplings that comply with API610, the standard for centrifugal pumps used in the petroleum industry.

Flexible friend

Flexible gear couplings consist of driving and driven hubs connected by a surrounding sleeve. Hubs have external gear teeth which mesh with internal teeth in the sleeve. The design is torsionally rigid yet can accommodate both angular and offset misalignment and axial forces, so finds applications in many different industries.

The R+W flexible gear couplings use a special crown gear tooth profile which minimises wear, allowing for a long, low maintenance life in many applications. Sizes are from 1300Nm to 348kNm.

Bendy bellows

With metal bellows couplings, the bellows style sleeve between the two hubs is flexible in several directions so can accommodate compound misalignments, yet provide an accurate, reliable drive. R&W bellows couplings feature highly flexible, high grade stainless steel bellows and high quality steel hubs. They are suitable for high torque applications and are based on a compact design that allows easy mounting/dismounting. Bellows couplings offer high misalignment compensation, yet are backlash free and torsionally rigid. The bellows element is available in various lengths and custom designs can be produced to exactly match the requirements of particular applications. Sizes are from 10 to 100kNm.

Tackling vibration

By incorporating an element made of an elastomeric material within the design of a coupling, it is possible to provide vibration damping and shock absorbing properties. R+W's elastomer based couplings include one with a split clamping hub, another with a keyway connection and one with a conical clamping ring, in sizes from 1.95 to 25kNm. Typical characteristics include high clamping forces, vibration damping, electrical isolation, backlash free rotation, and a press fit design.